Strong flow-acoustic resonances of rectangular cavities

Several studies relating to strongly resonating cavity shear layers in subsonic or supersonic flows are reviewed and discussed. Special consideration is given to cavity configurations which Rockwell and Naudascher (1978) branded "whistle-type" cavities, deep cavities and cavities mounted in the wall of an otherwise solid-walled duct (such as a wind tunnel). At certain flow conditions, each configuration can promote a strong, acoustic resonance which tends to favor a single dominant frequency in the pressure spectrum. The resultant shear layer motions and unsteady pressure fluctuations may be of large amplitude at the peak frequency. The empirical constants in Rossiter's formula and a similar frequency prediction formula for partially-covered cavities are also discussed.